146 FRIEND : NEW AND LITTLE-KNOWN OUGOCfcLETS. 



well into the teens. One sentence quoted above from Benham is 

 very puzzling. He says that Stylodrilus is one inch in length, or 

 'about one-third the size of an ordinary Tubifex? This would 



Tubife 



Beddard gives no hint as to 



the length, but a second species (T. blanchardi) is said to be about 

 25 mm., i.e. one inch in length, while Johnston says the length is 

 nearly one inch. Claparede states that T. bonneti Clap, (which 

 Beddard regards as identical with our species) is 3 to 3 J cm. long, or 

 a little upwards of an inch. There are three possible views of 

 Dr. Benham's expression. (1) It may be a slip of the pen for 

 Lumbrieulus, which does average three times the size of Stylodrilus. 

 (2) He may mean that Stylodrilus is one-third larger than an 

 ordinary Tubifex, which is also true. Or, what is also possible, he 

 may (3) be thinking of the larger of the two worms described by 

 Macintosh from the lakes of Scotland, which Beddard thinks is 

 certainly Tubifex rivulorum. My own specimens, collected in 

 Cumberland, Yorkshire, and Sussex, have never much exceeded one 

 inch, while the Cumbrian examples are usually under that length. 



Beddard has pointed out the confused state of our knowledge at 

 the present time, and allows two well defined species. Now that 

 they have been monographed we may hope to be able to get 

 a clearer idea of the subject. For the present I shall assume that 

 all the material which I have examined is to be referred to the older 

 pecies (T. rivulorum Lam.), and shall now proceed to describe the 

 worm, combining the published accounts with my own. 



I have collected the worm in the same localities as recorded for 

 Stylodrilus, namely on the banks of the Cocker and Derwent in 

 Cumberland, by the gas-works at Greengates near Apperley Bridge, 

 Yorkshire, as well as at Dallington in Sussex. The worm is usually 

 about an inch in length, of a bright red colour with straw-coloured 

 extremities. As Johnston accurately remarks, 'the skin is pellucid, 

 nnd permits us to trace easily the course of the dorsal vessel and of 

 the intestine, running tortuously from one end to the other, and 

 making a twist in every segment/ In the 8th segment there are 

 dilating hearts which form a prominent characteristic in several 

 species. In addition to the shorter forked setae there are a varying 

 number of capilliform or hair-shaped bristles in the dorsal bundles 

 of most of the anterior segments, which give the worm a most grace- 

 ful and striking appearance when seen for the first time under a low 

 power of the microscope. Beddard following Vejdovsky says that 

 the brain is concave in front with well marked lateral lobes. There 

 are no penial setae. The nervous system still needs examination, 

 and the whole of our British material should be carefully revised. 



: tura! 



